NSF Award
1215260
This Small Business Innovation Research Phase I project will demonstrate a highly efficient<br/>supersonic ejector vapor compression technology that converts low-to-medium grade thermal energy<br/>(200-400F) into useful refrigeration (20F-50F) at high condenser temperatures (100-120F). The proposed<br/>multi-fluid jet cooler maximizes heat transfer efficiency by using a propellant with relatively low latent to<br/>continuously entrain and compress an immiscible low temperature refrigerant of relatively high latent<br/>heat. Initial prototypes have 400% higher efficiencies than conventional single-fluid ejectors. Phase I<br/>research will extend these gains while operating at elevated condenser temperatures. Specific research<br/>foci are: 1) Highly efficient jet nozzles to supersonically expand a high molar mass, low specific heat<br/>ratio propellant without the expansion/compression losses observed when using conventional nozzle<br/>designs; 2) Mixing of subsonic refrigerant into the supersonic propellant with minimal kinetic energy loss<br/>by avoiding sonic choking of the refrigerant; and 3) Maximum pressure recovery diffusers utilizing weak,<br/>oblique compression waves instead of strong, normal shock waves to transition the mixed supersonic flow<br/>to subsonic velocity. Potential applications for the two-fluid ejector compression technology include<br/>natural gas powered air conditioning, concentrated solar thermal chiller plants, lower cost combined<br/>heating power and cooling plants, and thermally-driven water desalination.<br/><br/>The broader impact/commercial potential of this project is reduced economic and climate burden<br/>associated with the world?s growing demand for space cooling. Air conditioning is the leading usage for<br/>peak-time electricity in the U.S. and largest energy expense for commercial buildings. Globally, the<br/>$65billion air conditioning equipment market is growing at 5% p.a.; and because it is dominated by the<br/>electrically-driven mechanical vapor compression cycle the strain on electrical grids - and by extension<br/>the environment and economy - is rising likewise. A quiet, clean, reliable and cost effective heat-driven<br/>solution would greatly reduce these risks. Unfortunately, status quo technologies suffer low efficiencies,<br/>large form factors, and require expensive water-cooled condensers. Initial R&D efforts have proven an<br/>ejector vapor compressor using optimized fluid pairs built with low cost components can operate at<br/>efficiencies competitive with electric compressors when operating in moderate ambient conditions. Massmarket<br/>adoption, however, requires efficient operation at extreme outside temperatures. Phase I research<br/>will maximize cooling power and discharge pressure (thus operability at high condenser temperatures) by<br/>minimizing irreversible losses incurred during supersonic expansion and compression of the immiscible<br/>fluid pairs. Project findings will benefit adjacent fields of hypersonic avionics and low atmosphere jet<br/>propulsion
